Which organization announced a military exercise amid rising tensions with Russia?

Germany is the correct answer because it has been reported that, amid escalating tensions with Russia, the German armed forces have engaged in military exercises as part of their defense strategy and to enhance readiness. These exercises often aim to demonstrate military capabilities and strengthen partnerships with allies, particularly in areas where Russian aggression has raised concerns.

NATO, being a military alliance that includes Germany, often conducts joint exercises involving multiple member states, which might lead to confusion in associating military exercises directly with an individual country. The United Nations, on the other hand, focuses on diplomatic resolutions and peacekeeping missions rather than military exercises. The European Union is primarily an economic and political union with some security elements but does not conduct military exercises in the same way that national military forces do. Therefore, Germany's specific actions in this context make it the primary focus of military exercises responding to tensions with Russia.